Lopsided Growth at the Earth's Core

Apr 21, 2010
The inner core grows at the center of the Earth from crystallization of iron in the liquid outer core in such a way that solid iron permanently drifts eastward. Credit: Science/AAAS

What has twisted the Earth’s core so asymmetrically out of shape? That question has been a long-standing mystery for scientists, but two new studies are shining some light on the geodynamic processes that have shaped the core of our planet over the millennia, researchers report in the April 16 issue of Science.

Marc Monnereau and colleagues knew that the solid core at the center of the swells from the slow crystallization of iron in the outer core, so they began testing millions of different models of core growth, each involving various sizes of iron grains.

They settled on a model that takes into account the movement of iron from the solid central core to the liquid outer core—and they demonstrate how this convection of iron grains would lead to the permanent crystallization of the iron on one side of the core and continuous melting of the iron on the opposite side.

The researchers’ model shows exactly how this slow migration of iron in the inner core could lead to a melting Eastern hemisphere and a solid Western hemisphere in order to create the lopsided core we experience today. Since the process is still ongoing, this research also supports the theory of a relatively young inner core of the Earth.

In a separate study, Arwen Deuss and colleagues determined the structure of the Earth’s core using of 90 large earthquakes that occurred between 1976 and 2009.

Their data pinpoints specific regional variations in the structure of the core that are in addition to the hemispheric east-west lopsidedness, and may likewise be attributed to the preferential alignment of iron. On top of that, the patterns of variations these researchers found in the Earth’s core match up directly with the shape of the Earth’s magnetic field—a finding that suggests the core’s growth has been coupled to the planet’s since it first formed.

Explore further: Bridgmanite: World's most abundant mineral finally named

More information: -- Lopsided Growth of Earth's Inner Core, Marc Monnereau et al., Published Online April 15, 2010, Science DOI:10.1126/science.1186212
-- Regional Variation of Inner-Core Anisotropy from Seismic Normal-Mode Observations, Published Online April 15, 2010, Science DOI:10.1126/science.1188596

Source: American Association for the Advancement of Science

4.8 /5 (18 votes)

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User comments : 9

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fourthrocker
4.7 / 5 (3) Apr 21, 2010
Sounds like this might be related to the magnetic pole shift phenomena.
GDM
5 / 5 (2) Apr 21, 2010
an after effect from the collision that created the moon?
ebjh
2.7 / 5 (3) Apr 21, 2010
Does that explain why more quakes in the east and why Yellow Stone has't gone off yet
Mayday
3.7 / 5 (3) Apr 21, 2010
Could it be from the tiny black holes falling out of the LHC?
VOR
1 / 5 (1) Apr 21, 2010
there's a wacky idea that the earth has been growing in size and that techtonic plate shifting has been due more to that expansion. but
I never see anything really disproving the idea, since it would have playing out over the whole 5 bil yrs and it seems difficult to measure accurately. I wonder if any serious geologists are
investigating it.
MarkyMark
not rated yet Apr 22, 2010
Its probably caused by the top secret Anti alien Black hole gun the US operates [in before the nuts].

But seriously tho an interesting article.
StillWind
1 / 5 (3) Apr 25, 2010
there's a wacky idea that the earth has been growing in size and that tectonic plate shifting has been due more to that expansion. but
I never see anything really disproving the idea, since it would have playing out over the whole 5 bil yrs and it seems difficult to measure accurately. I wonder if any serious geologists are
investigating it.


This is not a "wacky" idea at all, and was originally proposed prior to the ridiculous "continental drift" theory. I can't imagine a more "wacky" theory than C.D.

The only real argument against E.E. is that geologists have not been able to measure an increase, and they are not able to come up with a mechanism by which the Earth grows. Neal Adams has produced an explanation as to how additional mass is produced in the core. As for measurements of growth, we simply have not been looking long enough.

Expanding Earth solves all the short comings of plate tectonics, and doesn't require the impossible scenarios that PT does.
mscir
not rated yet Apr 25, 2010
Very interesting article, thanks. The core and magnetic field are fascinating areas of study.
Ronan
not rated yet Apr 25, 2010
"Since the process is still ongoing, this research also supports the theory of a relatively young inner core of the Earth."
This sentence caught my eye; does this mean that the Earth's inner core has actually formed and been destroyed multiple times in the past? Or perhaps more prosaically, that different sides of the core have alternated between being formed and destroyed, allowing it to sort of "wobble" back and forth? VERY interesting article; I need to read up on this a good deal more.

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